Hydraulic chain tensioning means for tensioning the crawler chains of crawler vehicles

Abstract

A hydraulic chain tensioning means for automatically tensioning the chains of crawler vehicles equipped with two-, four- or eight-wheel articulated suspension means comprises essentially two tensioning cylinders (1.1 and 1.2) and a plurality of valves (3). The two tensioning cylinders (1.1 and 1.2) are interconnected by way of ducts (4) and connected by further ducts (5) to the valves (3). The tensioning cylinders (1.1 and 1.2) are fitted to the chassis (10) of the crawler vehicle and the leading wheel of the crawler vehicle bears against the piston rods (1.1K and 1.2K) of the tensioning cylinders (1.1 and 1.2). Parallel to the tensioning cylinders (1.1 and 1.2) a soft spring (piston-type accumulator 6) is connected so that at the beginning of the chain tensioning means being put under load only a minor pressure rise occurs in the tensioning cylinders (1.1 and 1.2).

We claim: 
     
       1. A hydraulic chain tensioner for automatically tensioning chains of a crawler vehicle, comprising: two tensioning cylinders having respective pistons supporting leading wheels of respective crawler chains of the vehicle and being fastened to a chassis thereof, said cylinders having first compartments behind said pistons and second compartments ahead of said pistons;   a first duct interconnecting said first compartments, a second duct interconnecting said second compartments;   a plurality of valves connected to said tensioning cylinders via said first duct and including: a pressure relief valve setting a maximum tensioning pressure p max  of said tensioning cylinders corresponding to a maximum tension applicable by said tensioning cylinders to said chains, and   a further valve connected to said first and second ducts and supplied from a source of hydraulic pressure for selectively pressurizing said first compartments to said maximum tensioning pressure p max  ; and     a soft spring connected in parallel to said tensioning cylinders for applying only a reduced tension to said chains at a start of load application to said tensioning cylinders, said soft spring comprising a hydropneumatic piston-type accumulator having: a hydraulic chamber connected by a third duct communicating with said first duct between said first compartments and said valves,   a gas space separated from said hydraulic chamber by an accumulator piston, said gas space being precompressed to a preliminary pressure p o  prior to operation of the chain tensioner of 2 to 10% of said maximum tensioning pressure p max , and   a mechanical end stop for said accumulator piston at an end of said accumulator opposite said hydraulic chamber.     
     
     
       2. The hydraulic chain tensioner defined in claim 1 wherein said gas space is at a preliminary pressure p o  prior to operation of the chain tensioner of 3 to 6.3% of said maximum tensioning pressure p max . 
     
     
       3. The hydraulic chain tensioner defined in claim 2 wherein said further valve is a 4/3 valve connecting said source and a tank to said first and second ducts, a nonreturn valve being connected between said 4/3 valve and said first duct, said hydraulic chain tensioner further comprising a pressure sensor connected to said first duct. 
     
     
       4. The hydraulic chain tensioner defined in claim 3, further comprising a safety valve between said hydropneumatic piston-type accumulator and said first duct which is switched into operation upon operation of the hydraulic chain tensioner.